#include <iostream>
#include <climits>
using namespace std;

int maximizeExpression(int A[], int n)
{
    int first[n + 1], second[n], third[n - 1], fourth[n - 2];

    for (int i = 0; i <= n - 3; i++) {
        first[i] = second[i] = third[i] = fourth[i] = INT_MIN;
    }

    first[n - 2] = second[n - 2] = third[n - 2] = INT_MIN;
    first[n - 1] = second[n - 1] = first[n] = INT_MIN;

    for (int i = n - 1; i >= 0; i--) {
        first[i] = max(first[i + 1], A[i]);
    }

    for (int i = n - 2; i >= 0; i--) {
        second[i] = max(second[i + 1], first[i + 1] - A[i]);
    }

    for (int i = n - 3; i >= 0; i--) {
        third[i] = max(third[i + 1], second[i + 1] + A[i]);
    }

    for (int i = n - 4; i >= 0; i--) {
        fourth[i] = max(fourth[i + 1], third[i + 1] - A[i]);
    }

    return fourth[0];
}

int main()

{
    int n;
    cin>>n;

    int arr[n];
    for(int i=0;i<n;i++){
        cin>>arr[i];
    }
     if (n >= 4) {
        cout << maximizeExpression(arr, n);
    }

    return 0;
}